In most situations, neutralization of an acid and an alkali is carried out in the bulk and the energy released in the form of heat. Here, we demonstrate that the neutralization energy of the two electrolytes can be directly utilized to produce electricity or split water with high efficiency. We reported a dual-electrolyte microfluidic fuel cell system (DEFC), which could stably deliver an open circuit voltage up to 1.76 V at room temperature under atmospheric pressure, and a peak power density of 145 mW/cm2, improved by 3 times compared with that in single electrolyte mode. When operated in the reverse mode, the microfluidic cell can be used for water electrolysis, demonstrating a water split voltage of ~0.74 V and a round trip voltage efficiency of 83.5% at a current density of 100 mA/cm2. The neutralization energy was both experimentally and theoretically proved to be well utilized as electrochemical energy in dual electrolyte systems at the electrodes both in fuel cell mode and water electrolyte mode. These results revealed that electrochemical neutralization can proceed if protons are consumed at the cathode and hydroxide ions reacted separately at the anode, accompanied by electron transfer via an external circuit. Given the DEFC's features of high open-circuit voltage, low water splitting voltage, and room-temperature operation condition, the reported DEFCs technology presents a superior route for high-efficiency energy conversion and storage system that could revolutionize the fields of large-scale energy storage and portable power systems.